1. Field of the Invention
The present invention relates to an engine generator and particularly to an engine generator capable of making efficient use of the engine power to produce a surplus of output with relation to greater load.
2. Description of the Related Art
It has widely been known to have a portable or mobile electric power source, such as an alternating current generator driven by an engine, equipped with an inverter apparatus for stabilizing its output voltage. A common engine generator includes a governor for controlling the number of revolutions of the engine by carrying out proportional, integral, and differential (PID) operations of a voltage corresponding to a deviation in the actual number of engine revolutions from the target value and determining the supply of fuel from the result of the operations. For example, the applicants of this invention, have developed and proposed a technique for monitoring a surplus of the electricity output of an engine generator equipped with a governor and determining the throttle opening for controlling the revolutions of engine to maintain a proper rate of the surplus of the electricity output (Japanese Patent Laid-open Heisei 11-308896).
When its maximum output is desired, the engine generator may operate with its throttle fully opened. If the load is increased during the full power operation, it will be an overload to the engine which is thus declined in the number of revolutions while running with the throttle fully opened. As the engine is declined in the power output, its driving force against the load will drop down. The drop down of the driving force may result in stalling of the engine.
For avoiding such an adverse effect, it is desired to open the throttle not fully for operation but with some redundancy. Without full throttle opening, the engine can hardly be operated at substantially its maximum power. Also, the engines tend to be overloaded at a specific range of revolutions depending on their types or may have biased characteristics for being overloaded at high temperatures.
It is an object of the present invention to provide an engine generator which can operate at substantially its maximum power even when the load is relatively great.
The first feature of this invention is in an engine generator which has an engine, a generator driven by the engine, and a throttle controlling means for controlling the throttle opening in the engine so that the output voltage of the generator converged to a predetermined target value, wherein an output voltage decreasing range which corresponds to a predetermined scale of the opening is assigned within a controllable range of the throttle opening, and when the throttle opening control comes into the output voltage decreasing range, the output voltage of the generator is made to decreased.
The second feature of this invention is in the engine generator in which an opening setting value provided from the throttle controlling means for controlling the throttle opening is arranged indicative of a load in the throttle opening controllable range, and when the throttle opening control comes into the output voltage decreasing range, the output voltage is made to decreased to a level determined by the opening setting value.
The third feature of this invention is in an engine generator which has a throttle controlling means for controlling the throttle opening in the engine according to a control data which is determined that the output voltage of the generator converged to a predetermined target value, wherein an output voltage decreasing range is assigned to exceed a controllable range of the throttle opening, and when the throttle opening control comes into the output voltage decreasing range, the output voltage of the generator is made to decreased in response to the control data which is arranged indicative of the output voltage decreasing range.
The forth feature of this invention is the engine generator in which the output voltage decreasing range is assigned extending to the controllable range of the throttle opening.
The fifth feature of this invention is in the engine generator in which the control data provided from the throttle controlling means for controlling the throttle opening is an opening setting value which is arranged indicative of a load in both the throttle opening controllable range and the range exceeding the throttle opening controllable range, and when the throttle opening control comes into the output voltage decreasing range, the output voltage is made to decreased in response to the opening setting value.
According to the first to fifth features, as the output voltage of the generator is made to decreased at the predetermined output voltage decreasing range, the load to the engine can be lowered. Particularly according to the first feature, the output voltage decreasing range is assigned within the controllable range of the throttle opening. According to the third feature, the output voltage decreasing range is assigned to exceed the controllable range of the throttle opening. According to the second or fifth feature, the output voltage decreasing range allows the output voltage to be controlled in response to the throttle opening setting which is indicative of the load; the greater the throttle opening, the lower the output voltage is made to decreased. According to the fourth feature, the output voltage decreasing range is extended from the throttle opening controllable range to the extra range exceeding the throttle opening controllable range, thus allowing the throttle opening control to be smoothly carried out between the two ranges.
The sixth feature of the present invention is that the output voltage decreasing range is sifted to its less loaded side determined by the throttle opening setting when the engine runs at a predetermined lower number of revolutions. The sixth feature allows the load to be lowered at the range where the number of engine revolutions is small.
The seventh feature of the present invention is that the output voltage decreasing range is sifted to its less loaded side determined by the throttle opening setting when the engine is overheated. The seventh feature allows the load to be lowered before the overheating results in overloading.